Grooved refractory brick construction



y 4, 1966 G. R. RIGBY 3,252,261

GROOVED REFRACTORY BRICK CONSTRUCTION Filed Nov. 29, 1963 2 Sheets-Sheet1 FIG. 6

PATENT AGENT y 4, 1966 G. R. RIGBY 3,252,261

GROOVED REFRACTORY BRICK CONSTRUCTION Filed Nov. 29, 1965 2 Sheets-Sheet2 PATENT AGENT United States Patent 3,252,261 GROOVED REFRACTORY BRICKCONSTRUCTION George R. Rigby, Lachute, Quebec, Canada, assignor toCanadian Refractories Limited, Montreal, Quebec, Canada Filed Nov. 29,1963, Ser. No. 326,684 3 Claims. (Cl. 52573) This application is acontinuation-in-part of United States application Serial No. 110,127,filed May 15, 1961, now abandoned. I

This invention relates to the construction of refractory brick used infurnace linings.

It is known in the art that the useful life of a refractory brick in afurnace lining is reduced by cracking due to the stresses which build upin brick as they are heated or cooled from one face. Ordinarily one faceor end of a brick is subjected to much higher temperatures than theopposite face or end of the brick and a temperature gradient exists inthe brick. With radical changes in temperature at the hot end,fluctuations in the gradient cause stresses which are frequentlyrelieved by cracking the brick.

Careful investigation has shown that the magnitude of the stressesdetermines the degree to which the cracking occurs resulting in spallingwith the loss of a portion of the brick.

When the end of a brick exposed in a furnace wall is subjected to thehigh furnace operating temperature, that end of the brick expandssubstantially while the opposite end remains for some time in itsoriginal condition. Thus heavy stresses are set up in the brick,particularly in its hot end. This results in spalling whichsubstantially reduces the useful life of the brick in the furnace liningand increases the cost of operating the furnace. Similar conditionsarise upon cooling.

The object of this invention is to provide a furnace wall structurewherein the tendency of the body of the brick in said wall to break awayor spall in use is greatly reduced.

A further object is to provide a construction which will avoid crackingof the individual bricks in such a structure due to internal stressesbuilt up during normal operation of the furnace.

In accordance with the invention, there is provided a furnace wallstructure having a hot face confronting the interior of the furnace anda cold face in opposed relation to the hot face. The wall structurecomprises a plurality of refractory bricks each having a pair of opposedplane side faces, a pair of opposed plane edge faces and a pair ofopposed plane end faces. Theperpendicular distance between the end facesbeing the major dimension of the brick and the perpendicular distancebetween the side faces being the minor dimension of the brick. One ofthe end faces of each b-rick constitutes a portion of-the hot face andsuch hot end face is uninterrupted. Each brick has a series of groovesinterrupting each face of at least one of the pairs of side and edgefaces, such side and edge faces being otherwise uninterrupted. Eachgroove is defined by a pair of side Walls and has a width notsubstantially more than inch and a depth not substantially less thaninch nor substantially more than inch. The medial plane between the sidewalls of each groove is at an angle of 0 to 45 to the plane of the hotend face. The walls of the groove closest to the hot end face are spacedtherefrom a distance of about inch to 2 inches. Each of the interruptedplane faces has a fiat portion between the grooves of each adjacent pairof grooves, each such flat portion having a dimension of the order ofone to one and one-half inches in a direction perpendiculatr to the endfaces of the brick. The walls of the groove closest to the cold end faceare at least 4 inches therefrom. The shortest distance between thebottom of any one of the grooves in one of the series and the bottom ofany one of the grooves in the other series is not less than 70% of theperpendicular distance between the interrupted plane faces.

The structure of the brick will now be described with reference to theaccompanying drawings in which,

FIGURE 1 is a perspective view of one form of the brick,

FIGURE 2 is a perspective view of another form;

FIGURE 3 is a cross-sectional view of a furnace structure embodyingbrick of the present invention,

FIGURE 3a is an enlarged perspective view of a portion of the furnacewall structure,

FIGURE 4 is a perspective view of another modified form of brick,

FIGURE 5 is a perspective view of a brick in accordance with theinvention in a met-a1 casing, and

FIGURES 6 and 7 are diagrams illustrative of modifications which thestructure of the brick may take.

In describing the brick construction the wide faces of the brick ,arereferred to as the sides (A-FIGURE l), the narrow faces as the edges(B--FIGURE 1), and the smallest faces at the hot end (CFIGURE 1) and thecold end opposite said hot end. By hot end is meant that end of thebrick which is adapted to be exposed to the interior of the furnace andby cold end the opposite end.

It has been found that the provision, as set forth, of grooves each notsubstantially more than @i preferably not more than Ma", in widthextending not substantially less than into the body of the brick and themedial plane between the side walls thereof being at an angle of 0 to 45to the plane of one end face of the brick greatly improves the spallingresistance of the brick. Optimum spalling resistance is obtained whenthe grooves extend into the brick not substantially more than The depthof the grooves as set forth applies to brick of any cross-sectional areaexcept that in no case should the grooves reduce the cross sectionalarea of the body of the brick by more than 30%, since, as previouslyindicated, this would increase the tendency to crack. When the groovesextend into the brick substantially less than the stress set up bytemperature fluctuations are not relieved sufiiciently to avoid crackingand spalling. Grooves which are located in planes which are not parallelto the end face of the brick must not be deeper than they would be whenlocated in planes parallel to the end face.

The grooves are located from 4-2 inches from the hot face of the brickand from each other. The preferred spacing range is 1-1 /2 inches. Thenumber of grooves depends upon the length of the brick, but it is notnecessary to carry them closer than 4 inches from the cold end of thebrick. At the outset of furnace operation, it is the groove or groovesnearest to the hot end which relieve stresses and prevent spalling. Thegrooves further removed from the hot end do not play an important partin relieving stresses until the brick is reduced in length throughservice.

Grooves located in the edge of the brick give better re sults than whenlocated in the sides and are preferably located in planes parallel tothe hot end and face of the brick.

It is not necessary to have the same number of grooves on opposite facesand the grooves in one face may be staggeredin relation to those in theother. Grooves, running longitudinally of the brick are not effective.

Grooves in the hot end face of the brick are not of value because theyexpose additional area in this face which is subject to slag attack.

The narrow grooves may be formed by cutting with a saw or by using amould having internal projections of the required dimensions on itsinner walls. In forming the narrow grooves by moulding, the projectionson the mould are preferably V-shaped, about wide at the base andextending inwardly about When the narrow grooves are formed by cuttingwith a saw best results are obtained when the cuts are made beforeburning the brick.

FIGURE 1 shows a brick having five narrow grooves 1 in each edge of thebrick running substantially parallel to its ends and extending inwardlyabout The grooves are spaced apart about 1" and the initial space or cut1a is about 1" from the hot face of the brick. The grooves were formedby cutting before burning.

FIGURE 2 shows a brick having four narrow grooves 1 in each edge and twonarrow grooves 2 in each of the sides A running substantially parallelto the edges of the brick. As shown, one groove 3 is located between thepair of grooves adjacent the hot end and one groove 2 is located betweenthe pair of grooves 1 remote from the hot end.

FIGURE 3 is a diagrammatic view of a conventional form of furnace '10having side walls 11 and roof 12. The interior or hot face of thefurnace is indicated at 13. The walls 11 comprise a plurality of bricks14 having grooves 1 therein in accordance with the invention. The roof12 comprises a plurality of bricks 15 also having grooves 1 therein inaccordance with the invention. FIGURE 3a illustrates more clearly thelocation of the grooves 1 and 2 with respect to the hot face 13. It willbe apparent that, in the wall structure, the grooves 1 and 2 are notlocated in any exposed face of the brick but rather in a face adjoininganother brick or other structural element.

It will also be appreciated that the brick of the present invention arelaid as headers, i.e., a brick laid on fiat with its longitudinaldimension perpendicular to the face of the wall.

While the structure illustrated is of self-supporting nature, the brickof the present invention may be employed in externally supported wallsand suspended arches.

The brick of FIGURE 4 illustrates the use of narrow grooves 4 inV-shaped form, as described above, and positioned in the same manner asgrooves 1 in FIGURE 1.

FIGURE 5 shows a brick similar to that of FIGURE 1 having a U-shapedmetal casing 5 with internal projections 6 which upon forming the brickby moulding produce spaces in the brick which are occupied by theprojections. The inwardly projecting lugs 6 serve to anchor the casingto the brick in a well known manner. It will be apparent that the metalcasing may be of other form and need only contact the two edges in whichthe grooves are formed or the brick may be wholly enclosed in metal.

FIGURE 6 diagrammatically shows the angular dis position of the grooveswhen they are located in the edges of the brick and are perpendicular tothe sides of the brick. When the groove 7 is at 45 to the edge of thebrick it occupies the plane D E F at angle X or D E H at angle Z. Whenangles X and Z become 90 the groove occupies the plane D E G which isshown in FIGURE 2.

Similarly FIGURE 7 shows the angular disposition of the grooves whenthey are located in and perpendicular to the sides of the brick. Whenthe groove 8 is at 45 to the edge of the brick it occupies the plane I KL at angle Y or J KM at angle W.

Thus, it will be recognized that any of the described angulardispositions of the planes of the grooves or any combination thereof maybe used in making the brick.

In determining the capacity of this brick structure to resist thedisruptive influence of internal stresses developed therein during usein a furnace, the brick structure was subjected to what applicantdefines as Wicket Spall 7 Test, as follows:

It consists of subjecting the end face of a brick alternately to (1)radiation from a furnace wall at 1100 C. and at a distance of 2 inchesfor 45 minutes, and (2) a blast of air at room temperature for 15minutes. The cycle is repeated until either the end of the brick breaksoff or it remains whole after 10 cycles, when it is assessed visually asto the severity of the damage incurred in the test. Ten cycles is thenormal duration of the test, since it has been found that thisrepresents adequate spalling resistance for most service conditions.Brick made of magnesia materials under this test have, on the aver-age,spalled at 1 to 3 cycles. Brick made of chrome ore spall in the samerange, whereas brick made from chrome ore and 20-30% magnesia spalled at3 to 4 cycles.

Brick of the construction herein described and shown and made of thesetypes of materials, having a plurality of narrow grooves arrangedasdescribed and shown have remained intact after an excess of 10 cycles.Brick of the structure shown in FIGURES l and 4 have been found toresist spalling after as many as 30 cycles although after 14 cyclesthere was evidence of small cracks in some cases. The brick structure ofFIGURE 2, having the grooves in the sides as well as in the edges,withstood 30 cycles.

To further illustrate the effect of angular disposition of the grooves,as described with reference to FIGURES 6 and 7 the following table isincluded, showing the variety of angles at which the grooves may bedisposed in relation to the respective faces of the brick and the resultof the Wicket Spall Test described. For satisfactory spalling resistancefigures 10 is a minimum. The signs are an indication of the relativemerits of those tests that have not spalled in 10 cycles with indicatingbrick likely to go 30 or more cycles.

Spalling results on brick with grooves at various angles Angle of Angleof Test Groove Spall Data Groove Spall Data (Angle X (Angle Y Figure 6)Figure 7) 1 No grooves.

The orientation of a groove can best be described by reference to themedial plane which is the plane midway between the two planes in whichthe major walls of the groove lie.

In the accompanying claims, the expression wall structure includes theroof structure as well as the side walls of the furnace.

I claim:

1. A furnace comprising a wall structure having a hot face confrontingthe interior of said furnace and a cold face in opposed relation to saidhot face, said wall structure comprising a plurality of refractorybricks each having a pair of opposed plane side faces, a pair of opposedplane edge faces, and a pair of opposed plane end faces, theperpendicular distance between said end faces being the major dimensionof said brick and the perpendicular distance between said side facesbeing the minor dimension of said brick, each said brick having a firstone of said end faces exposed to the interior of said furnace andconstituting a portion of said hot face and a second one of said endfaces constituting a portion of said cold face, said first end facebeing uninterrupted, each said brick having a series of groovesinterrupting each said plane face of at least one of said pairs of sideand edge faces, said side and edge faces being otherwise uninterrupted,a pair of side walls defining each said groove, each said groove havinga width not substantially more than inch and a depth not substantiallyless than inch nor substantially more than inch, the medial planebetween said side walls of each said groove being at an angle of 0 to 45to the plane of said first end face,

said walls of the one of said grooves closest to said first end facebeing spaced from said first end face a distance of about inch to 2inches, each said interrupted plane face having a flat portion extendingbetween said grooves of each adjacent pair of said grooves, each saidflat portion having a dimension of the order of one to one and onehalfinches in a direction perpendicular to said end 'faces, said walls ofthe one of said grooves closest to said second end face being at least 4inches therefrom, and the shortest distance between the bottom of anyone of said grooves in one of said series and the bottom of any one ofsaid grooves in the other one of said series being not less than 70% ofthe perpendicular distance between said interrupted plane faces.

2. A furnace Wall structure as defined in claim 1 wherein each saidgroove is V-shaped in cross-section.

3. A furnace wall structure as defined in claim 1 wherein a series ofsaid grooves is provided in each of said side and edge faces.

References Cited by the Examiner UNITED STATES PATENTS FRANK L. ABBOTT,Primary Examiner.

HENRY C. SUTHERLAND, Examiner.

D. R. COMUZZIE, Assistant Examiner.

1. A FURNACE COMPRISING A WALL STRUCTURE HAVING A HOT FACE CONFRONTINGTHE INTERIOR OF SAID FURNACE AND A COLD FACE IN OPPOSED RELATION TO SAIDHOT FACE, SAID WALL STRUCTURE COMPRISING A PLURALITY OF REFRACTORYBRICKS EACH HAVING A PAIR OF OPPOSED PLANE SIDE FACES, A PAIR OF OPPOSEDPLANE EDGES FACES, AND A PAIR OF OPPOSED PLANE END FACES, THEPERPENDICULAR DISTANCE BETWEEN SAID END FACES BEING THE MAJOR DIMENSIONOF SAID BRICK AND THE PERPENDICULAR DISTANCE BETWEEN SAID SIDE FACESBEING THE MINOR DIMENSION OF SAID BRICK, EACH SAID BRICK HAVING A FIRSTONE OF SAID END FACES EXPOSED TO THE INTERIOR OF SAID FURNACE ANDCONSTITUTING A PORTION OF SAID HOT FACE AND A SECOND ONE OF SAID ENDFACES CONSTITUTING A PORTION OF SAID COLD FACE, SAID FIRST END FACEBEING UNINTERRUPTED, EACH SAID BRICK HAVING A SERIES OF GROOVESINTERRUPTED, EACH SAID PLANE FACE OF AT LEAST ONE OF SID PAIRS OF SIDEAND EDGE FACES, SAID SIDE AND EDGE FACES BEING OTHERWISE UNINTERRUPTED,A PAIR OF SIDE WALLS DEFINING EACH SAID GROOVE, EACH SAID GROOVE HAVINGA WIDTH NOT SUBSTANTIALLY MORE THAN 5/16 INCH AND A DEPTH NOTSUBSTANTIALLY LESS THAN 11/32 INCH NOR SUBSTANTIALLY MORE THAN 17/32INCH, THE MEDIAL PLANE BETWEEN SAID SIDE WALLS OF EACH SAID GROOVE BEINGAT AN ANGLE OF 0* TO 45* TO THE PLANE OF SAID FIRST END FACE, SAID WALLSOF THE ONE OF SAID GROOVES CLOSEST TO SAID FIRST END FACE BEING SPACEDFROM SAID FIRST END FACE A DISTANCE OF ABOUT 3/4 INCH TO 2 INCHES, EACHSAID INTERRUPTED PLANE FACE HAVING A FLAT PORTION EXTENDING BETWEEN SAIDGROOVES OF EACH ADJACENT PAIR OF SAID GROOVES, EACH SAID FLAT PORTIONHAVING A DIMENSION OF THE ORDER OF ONE TO ONE AND ONEHALF INCHES IN ADIRECTION PERPENDICULAR TO SAID END FACES, SAID WALLS OF THE ONE OF SAIDGROOVES CLOSEST TO SAID SECOND END FACE BEING AT LEAST 4 INCHESTHEREFROM, AND THE SHORTEST DISTANCE BETWEEN THE BOTTOM OF ANY ONE OFSAID GROOVES IN ONE OF SAID SERIES AND THE BOTTOM OF ANY ONE OF SAIDGROOVES IN THE OTHER ONE OF SAID SERIES BEING NOT LESS THAN 70% OF THEPERPENDICULAR DISTANCE BETWEEN SAID INTERRUPTED PLANE FACES.